EP0887714A2 - Développement d'un image électrostatique - Google Patents

Développement d'un image électrostatique Download PDF

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Publication number
EP0887714A2
EP0887714A2 EP98304855A EP98304855A EP0887714A2 EP 0887714 A2 EP0887714 A2 EP 0887714A2 EP 98304855 A EP98304855 A EP 98304855A EP 98304855 A EP98304855 A EP 98304855A EP 0887714 A2 EP0887714 A2 EP 0887714A2
Authority
EP
European Patent Office
Prior art keywords
image
latent image
electrostatic latent
imaging member
layer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP98304855A
Other languages
German (de)
English (en)
Other versions
EP0887714B1 (fr
EP0887714A3 (fr
Inventor
Chu-Heng Liu
Weizhong Zhao
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Xerox Corp
Original Assignee
Xerox Corp
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Filing date
Publication date
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Publication of EP0887714A2 publication Critical patent/EP0887714A2/fr
Publication of EP0887714A3 publication Critical patent/EP0887714A3/fr
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Publication of EP0887714B1 publication Critical patent/EP0887714B1/fr
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Expired - Lifetime legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/22—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20
    • G03G15/34—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which the powder image is formed directly on the recording material, e.g. by using a liquid toner
    • G03G15/342—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which the powder image is formed directly on the recording material, e.g. by using a liquid toner by forming a uniform powder layer and then removing the non-image areas
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/22—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20
    • G03G15/34—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which the powder image is formed directly on the recording material, e.g. by using a liquid toner
    • G03G15/344—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which the powder image is formed directly on the recording material, e.g. by using a liquid toner by selectively transferring the powder to the recording medium, e.g. by using a LED array
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G2217/00—Details of electrographic processes using patterns other than charge patterns
    • G03G2217/0041—Process where the image-carrying member is always completely covered by a toner layer
    • G03G2217/0058—Process where the image-carrying member is always completely covered by a toner layer where the toner layer is being charged
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G2217/00—Details of electrographic processes using patterns other than charge patterns
    • G03G2217/0041—Process where the image-carrying member is always completely covered by a toner layer
    • G03G2217/0066—Process where the image-carrying member is always completely covered by a toner layer where no specific pick-up of toner occurs before transfer of the toner image

Definitions

  • This invention relates generally to electrostatic latent image development, and, more particularly, concerns an apparatus and method for developing an electrostatic latent image having a layer of developing or toner material coated thereon by selectively applying a charge potential to the layer to create an image-wise charged toner layer capable of being developed and selectively separated and transferred, thereby producing an output image corresponding thereto.
  • the present invention specifically contemplates a novel electrostatographic imaging process wherein an electrostatic latent image bearing member having a layer of marking material or toner particles coated thereon is selectively charged in an imagewise manner to create a secondary latent image corresponding to the electrostatic latent image on the imaging member.
  • Image-wise charging is accomplished by a wide beam charge source for introducing free mobile charges or ions in the vicinity of the electrostatic latent image coated with the layer of marking material or toner particles.
  • the latent image causes the free mobile charges or ions to flow in an image-wise ion stream corresponding to the latent image.
  • the latent image carrying toner layer is subsequently developed by selectively separating and transferring image areas of the toner layer to a copy substrate for producing an output document.
  • the present invention contemplates an imaging apparatus, wherein an electrostatic latent image including image and non-image areas is formed in a layer of marking material, and further wherein the latent image can be developed by selectively separating portions of the latent image bearing layer of marking material such that the image areas reside on a first surface and the non-image areas reside on a second surface.
  • the invention can be defined as an image development apparatus, comprising a system for generating a first electrostatic latent image on an imaging member, wherein the electrostatic latent image includes image and non-image areas having distinguishable charge potentials, and a system for generating a second electrostatic latent on a layer of marking materials situated adjacent the first electrostatic latent image on the imaging member, wherein the second electrostatic latent image includes image and non-image areas having distinguishable charge potentials of a polarity opposite to the charge potentials of the charged image and non-image areas in the first electrostatic latent image.
  • US-A-5,436,706 discloses an imaging apparatus including a first member having a first surface having formed thereon a latent electrostatic image, wherein the latent electrostatic image includes image regions at a first voltage and background regions at a second voltage.
  • a second member charged to a third voltage intermediate the first and second voltages is also provided, having a second surface adapted for resilient engagement with the first surface.
  • a third member is provided, adapted for resilient contact with the second surface in a transfer region.
  • the imaging apparatus also includes an apparatus for supplying liquid toner to the transfer region thereby forming on the second surface a thin layer of liquid toner containing a relatively high concentration of charged toner particles, as well as an apparatus for developing the latent image by selective transferring portions of the layer of liquid toner from the second surface to the first surface.
  • an image development apparatus comprising means for image-wise charging of a toner layer by a wide beam charging source capable of introducing free mobile charges or ions in the vicinity of an electrostatic latent image coated with layer of developing material, whereby the latent image causes the free mobile charges or ions to flow in an image-wise charge or ion stream corresponding to the latent image.
  • Means are also provided for developing the latent image carrying toner layer and transferring the developed toner layer to a copy substrate for producing an output document.
  • an imaging apparatus comprising an imaging member for having an electrostatic latent image formed thereon.
  • the imaging member includes a surface capable of supporting a layer of marking material which may be in the form of toner particles.
  • An imaging device is also provided for generating the electrostatic latent image on the imaging member, wherein the electrostatic latent image includes image areas defined by a first charge voltage and non-image areas defined by a second charge voltage distinguishable from the first charge voltage.
  • a marking material supply apparatus is also provided for depositing marking material on the surface of the imaging member to form a layer of marking material thereon adjacent the electrostatic latent image on the imaging member.
  • a charge source is provided for selectively delivering charges to the layer in an image-wise manner responsive to the electrostatic latent image on the imaging member to form a secondary latent image in the marking material layer having image and non-image areas corresponding to the electrostatic latent image on said imaging member.
  • a separator member is also provided for selectively separating portions of the layer of marking material in accordance with the secondary latent image in the layer of marking material to create a developed image corresponding to the electrostatic latent image formed on said imaging member.
  • an imaging process comprising the steps of: generating an electrostatic latent image on an imaging member having a surface capable of supporting marking material, wherein the electrostatic latent image includes image areas defined by a first charge voltage and non-image areas defined by a second charge voltage distinguishable from the first charge voltage; depositing marking material on the surface of the imaging member to form a layer of marking material thereon adjacent the image and non-image areas of the electrostatic latent image; selectively delivering charges or ions to the layer of marking material in an image-wise manner responsive to the electrostatic latent image on the imaging member for forming a secondary latent image in the layer of marking material, having image and non-image areas corresponding to the electrostatic latent image on the imaging member; and selectively separating and transferring portions of the layer of marking material from the imaging member in accordance with the secondary latent image therein for creating a developed image corresponding to the electrostatic latent image formed on the imaging member.
  • an imaging apparatus comprising means for creating an electrostatic latent image including image and non-image areas in a toner layer, and means for developing or selectively separating the latent image bearing toner layer such that the image areas reside on a first surface and the non-image areas reside on a second surface.
  • an imaging process comprising the steps of creating an electrostatic latent image including image and non-image areas in a toner layer on an electrostatic latent image bearing member, and selectively separating the latent image in the toner layer such that the image areas reside on a first surface and the non-image areas reside on a second surface.
  • an image development apparatus comprising means for generating a first electrostatic latent image on an imaging member, wherein the electrostatic latent image includes image and non-image areas having distinguishable charge potentials, and means for generating a second electrostatic latent image on a toner layer situated adjacent the first electrostatic latent image on the imaging member, wherein the second electrostatic latent image includes image and non-image areas having distinguishable charge potentials of a polarity opposite to the charge potentials of the charged image and non-image areas in the first electrostatic latent image.
  • a process for image development comprising the steps of generating a first electrostatic latent image on an imaging member, wherein the electrostatic latent image includes image and non-image areas having distinguishable charge potentials; and generating a second electrostatic latent on a toner layer situated adjacent the first electrostatic latent image on the imaging member, wherein the second electrostatic latent image includes image and non-image areas having distinguishable charge potentials of a polarity opposite to the charge potentials of the charged image and non-image areas in the first electrostatic latent image.
  • an image development apparatus comprising means for image-wise charging of a toner layer by introducing free mobile ions in the vicinity of an electrostatic latent image coated with a layer of developing material, whereby the latent image causes the free mobile ions to flow to the toner layer in an image-wise ion stream corresponding to the latent image, thereby creating a secondary latent image in the toner layer.
  • Means are also provided for developing the secondary latent image by selectively separating portions thereof from the imaging member and further transferring the developed image to a copy substrate for producing an output document.
  • an image development apparatus comprising an imaging member including an imaging surface having a layer of marking material thereon, and means for creating an electrostatic latent image in the layer of marking material.
  • an image development process for developing an image on an imaging member comprising the steps of providing a layer of marking material on a surface of the imaging member, and generating an electrostatic latent image in the layer of marking material.
  • Imaging apparatus capable of image-wise toner charging in accordance with the present invention is shown, comprising an assemblage of operatively associated image forming elements, including an imaging member 10 situated in contact with an image separating member 20 at an image separating nip 12 formed therebetween.
  • Imaging member 10 includes an imaging surface of any type capable of having an electrostatic latent image formed thereon.
  • An exemplary imaging member 10 may include a typical photoconductor or other photoreceptive component of the type known to those of skill in the art in electrophotography, wherein a surface layer having photoconductive properties is supported on a conductive support substrate.
  • an imaging member as are well known in the art of electrostatographic printing, including, for example, but not limited to, non-photosensitive imaging members such as a dielectric charge retaining member of the type used in ionographic printing machines, or electroded substructures capable of generating charged latent images.
  • non-photosensitive imaging members such as a dielectric charge retaining member of the type used in ionographic printing machines, or electroded substructures capable of generating charged latent images.
  • Imaging member 10 is rotated, as indicated by arrow 11, so as to transport the surface thereof in a process direction for implementing a series of image forming steps in a manner similar to typical electrostatographic printing processes.
  • a charging station which may include a corona generating device 30 or any other charging apparatus for applying an electrostatic charge to the surface of the imaging member 10.
  • the corona generating device 30 is provided for charging the photoconductive surface of imaging member 10 to a relatively high, substantially uniform potential.
  • various charging devices such as charge rollers, charge brushes and the like, as well as induction and semiconductive charge devices among other devices which are well known in the art may be utilized at the charging station for applying a charge potential to the surface of the imaging member 10.
  • the imaging member 10 After the imaging member 10 is brought to a substantially uniform charge potential, the charged surface thereof is advanced to an image exposure station, identified generally by reference numeral 40.
  • the image exposure station projects a light image corresponding to the input image onto the charged photoconductive surface.
  • the light image projected onto the surface of the imaging member 10 selectively dissipates the charge thereon for recording an electrostatic latent image on the photoconductive surface.
  • the electrostatic latent image comprises image areas defined by a first charge voltage and non-image areas defined by a second charge voltage, in image configuration corresponding to the input image informational areas.
  • the image exposure station 40 may incorporate various optical image formation and projection components as are known in the art, and may include various well known light lens apparatus or digital scanning systems for forming and projecting an image from an original input document onto the imaging member 10. Alternatively, various other electronic devices available in the art may be utilized for generating electronic information to create the electrostatic latent image on the imaging member. It will be understood that the electrostatic latent image may be comprised of image and non-image areas that are defined areas having opposite charge polarities or by areas that merely have first and second distinguishable charge levels.
  • a layer of charged or uncharged marking or toner particles is deposited on the entire surface of the latent image bearing imaging member 10.
  • a toner supply apparatus or applicator 50 is provided, as depicted in the exemplary embodiment of Figure 1, whereby a layer of charged or uncharged marking or toner particles (and possibly some carrier mechanism such as a liquid solvent) is transported onto the surface of the imaging member 10.
  • the exemplary embodiment of Figure 1 shows an illustrative toner applicator 50, wherein a housing 52 is adapted to accommodate a supply of toner particles 54 and any additional carrier material, if necessary.
  • the toner applicator 50 includes an applicator roller 56 which is rotated in a direction as indicated by arrow 57 to transport toner from housing 52 into contact with the surface of the imaging member 10, forming a substantially uniformly distributed layer of toner, or a so-called "toner cake", 58 thereon.
  • the toner cake described above can be created in various ways. For example, depending on the materials utilized in the printing process, as well as other process parameters such as process speed and the like, a layer of toner particles having sufficient thickness, preferably on the order of between 2 and 15 microns and more preferably between 3 and 8 microns, may be formed on the surface of the imaging member 10 by merely providing adequate proximity and/or contact pressure between the applicator roller 56 and the imaging member 10. Alternatively, electrical biasing may be employed to assist in actively moving the toner particles onto the surface of the imaging member 10.
  • the applicator roller 56 can be coupled to an electrical biasing source 55 for implementing a so-called forward biasing scheme, wherein the toner applicator 56 is provided with an electrical bias of magnitude greater than both the image and non-image (background) areas of the electrostatic latent image on the imaging member 10, thereby creating electrical fields extending from the toner applicator roll 56 to the surface of the imaging member 10. These electrical fields cause toner particles to be transported to imaging member 10 for forming a substantially uniform layer of toner particles on the surface thereof.
  • toner layer 58 may be utilized for applying toner layer 58 to the surface of the imaging member, including various well known apparatus analogous to development devices used in conventional electrostatographic applications, such as, but not limited to: powder cloud systems which transport developing material to the imaging member by means of a gaseous medium such as air; brush systems which transport developing material to the imaging member by means of a brush or similar member; and cascade systems which transport developing material to the imaging member by means of a system for pouring or cascading the toner particles onto the surface of the imaging member.
  • powder cloud systems which transport developing material to the imaging member by means of a gaseous medium such as air
  • brush systems which transport developing material to the imaging member by means of a brush or similar member
  • cascade systems which transport developing material to the imaging member by means of a system for pouring or cascading the toner particles onto the surface of the imaging member.
  • various systems directed toward the transportation of liquid developing material having toner particles immersed in a carrier liquid can be incorporated into the present invention.
  • liquid transport system can include a fountain-type device as disclosed generally in commonly assigned U.S. Patent No. 5,519,473 (incorporated by reference herein), or any other system capable of causing a flow of liquid developing material, including toner particles immersed in a liquid carrier medium, onto the surface of the imaging member. It is noted that, in the case of liquid developing materials, it is desirable that the toner cake formed on the surface of the imaging member 10 should be comprised of at least approximately 10% by weight toner solids, and preferably in the range of 15% - 35% by weight toner solids.
  • the presence of the latent image on the imaging member may generate some fringe fields in areas of interface between image and non-image areas of the latent image.
  • these fringe fields are minimal relative to the fields associated with conventional electrostatic latent image development such that, although some toner layer nonuniformity may result, the toner layer generated on the imaging member surface can be characterized as having a substantially uniform density per mass area in both image and background areas of the latent image.
  • the toner layer be uniform or even substantially uniformly distributed on the surface of the imaging member 10, so long as the toner layer covers, at a minimum, the desired image areas of the latent image.
  • the toner layer 58 is formed on the surface of the electrostatic latent image bearing imaging member 10, the toner layer is charged in an image-wise manner.
  • a charging device 60 represented schematically in Figure 1 as a well known scorotron device, is provided for introducing free mobile ions in the vicinity of the charged latent image, to facilitate the formation of an image-wise ion stream extending from the source 60 to the latent image on the surface of the image bearing member 10, as will be described.
  • the image-wise ion stream generates a secondary latent image in the toner layer made up of oppositely charged toner particles in image configuration corresponding to the latent image.
  • the process of generating a secondary latent image in the toner cake layer will be described in greater detail with respect to Figure 2, where the initially charged toner cake 58 is illustrated, for purposes of simplicity only, as a uniformly distributed layer of negatively charged toner particles having the thickness of a single toner particle.
  • the toner cake resides on the surface of the imaging member 10 which is being transported from left to right past the broad source ion charging device 60.
  • the primary function of the broad source ion charging device 60 is to provide free mobile ions in the vicinity of the imaging member 10 having the toner layer and latent image thereon.
  • the broad source ion device may be embodied as various known devices, including, but not limited to, any of the variously known corona generating devices available in the art, as well as charging roll type devices, solid state charge devices and electron or ion sources analogous to the type commonly associated with ionographic writing processes.
  • a scorotron type corona generating device is utilized.
  • the scorotron device comprises a corona generating electrode 62 enclosed within a shield member 64 surrounding the electrode 62 on three sides.
  • a wire grid 66 covers the open side of the shield member 64 facing the imaging member 10.
  • the corona generating electrode 62 otherwise known as a coronode, is coupled to an electrical biasing source 63 capable of providing a relatively high voltage potential to the coronode, which causes electrostatic fields to develop between the coronode 62 and the grid and the imaging member 10.
  • the scorotron grid 66 is biased so as to be operative to control the amount of charge and the charge uniformity applied to the imaging surface 10 by controlling the flow of ions through the electrical field formed between the grid and the imaging surface.
  • the function of the charging device 60 is to charge the toner layer 58 in an image-wise manner.
  • This process will be described with respect to a negatively charged toner layer, although it will be understood that the process can also be implemented using a positively charged toner layer.
  • the process of the present invention can also be implemented using an uncharged or neutral toner layer, as will be described in greater detail as the present description proceeds.
  • the process of the present invention requires that ion source 60 provide ions having a charge opposite the toner layer charge polarity.
  • the scorotron 60 is preferably provided with an energizing bias at grid 66 intermediate the potential of the image and non-image areas of the latent image on the imaging member 10.
  • the energizing bias at the grid 66 can be higher or lower than the bias of the image and non-image areas of the latent image.
  • the energizing bias applied to grid 66 can be provided in the form of either a direct current (DC) electrical bias or an alternating current (AC) bias having a DC offset.
  • the bias potential in areas where the latent image is at a potential lower than the bias potential of the charging source grid 66, the bias potential generates electrostatic field lines in a direction toward the imaging member 10 and toner layer 58 thereon. Conversely, electrostatic field lines are generated in a direction away from the imaging member 10 and toner layer 58 thereon in areas where the latent image is at a potential higher than the bias potential of the charging source grid 66.
  • Figure 2 illustrates the effect of the field lines in the case of an ion source energized by an AC voltage having a DC grid bias 66 voltage intermediate to the image and non image areas of the latent image, represented by (+) and (-) signs, respectively, on the back side of the imaging member 10.
  • positive ions flow from the ion source 60 in the direction of the field lines while negative ions (electrons) flow in a direction opposite to the direction of the field lines such that he positive ions presented in the vicinity of a positively charged area of the latent image are repelled from the toner layer 58 while the positive ions in the vicinity of a negatively charged area of the latent image are attracted to the toner layer, and captured thereby.
  • a charged toner layer is situated on a latent image bearing imaging member, wherein the charged toner layer is exposed to charged ions for selectively reversing the preexisting charge of the toner layer.
  • fringe fields illustrated as field lines extending between image and non-image regions of the latent image can affect the uniformity of the charged toner cake. While the existence of these fringe fields may be advantageous if the fringe fields can be properly controlled, these fringe fields may manifest themselves as image quality defects in the final output document.
  • the present invention contemplates an alternative embodiment to the image-wise toner layer charging process described hereinabove, wherein the fringe field effect may be eliminated.
  • the image-wise toner charging process of the present invention may be carried out using a neutrally charged toner cake layer coated on the imaging member.
  • an ion source or multiple ion sources, must be provided for presenting both negative and positive polarity ions to the toner layer in the vicinity of the latent image for oppositely charging regions of the toner layer corresponding to image and non image areas of the latent image.
  • an AC driven scorotron device can be used to provide ions of opposite polarity.
  • independent ion sources capable of providing opposite polarity ions can be used.
  • independent broad source ion generating devices as variously known in the art may be incorporated, either as a single AC driven device capable of providing both positive and negative charge ions, or as a pair of DC driven devices for providing the same.
  • the ion sources are provided in the form of first and second corona generating devices 67 and 68, each independently driven by DC biasing sources 63 to provide oppositely charged ion streams.
  • This embodiment operates in a manner similar to the embodiment of Figure 2, wherein positive ions generated by ion source 67 in the vicinity of a positively charged area of the latent image are repelled by the underlying latent image, while the positive ions in the vicinity of negatively charged areas of the latent image are attracted to the imaging member 10 and captured by the toner layer.
  • negative ions generated by ion source 68 are absorbed or captured by the neutral toner particles adjacent positively charged areas of the latent image, while negative ions in the vicinity of a negatively charged areas of the latent image are repelled by the latent image.
  • the free flowing ions generated by ion sources 67 and 68 are selectively captured by toner layer 58 in accordance with the charge of the latent image areas on the imaging member. This process induces image-wise charging of the toner layer 58, creating a secondary latent image within toner layer 58 made up of image and background areas which are charged oppositely with respect to the charge of the original latent image on the imaging member 10.
  • the charge of the original latent image may be converted into the secondary latent image in the toner layer such that the original electrostatic latent image is substantially or completely dissipated into the toner layer after the image-wise toner charging process is complete.
  • image separator 20 may be provided in the form of a biased roll member having a surface adjacent to the surface of the imaging member 10 and preferably contacting the toner layer 58 residing on image bearing member 10.
  • An electrical biasing source is coupled to the image separator 20 to bias the image separator 20 so as to attract either image or non-image areas of the latent image formed in the toner layer 58 for simultaneously separating and developing the toner layer 58 into image and non-image portions.
  • the image separator 20 is biased with a polarity opposite the charge polarity of the image areas in the toner layer 58 for attracting image areas therefrom, thereby producing a developed image made up of selectively separated and transferred portions of the toner cake on the surface of the image separator 20, while leaving background image byproduct on the surface of the imaging member 10.
  • the image separator 20 can be provided with an electrical bias having a polarity appropriate for attracting non-image areas away from the imaging member 10, thereby maintaining toner portions corresponding to image areas on the surface of the imaging member, yielding a developed image thereon, while removing non-image or background areas with the image separator 20.
  • the developed image may then be transferred to a copy substrate 70 via any means known in the art, which may include an electrostatic transfer apparatus including a corona generating device of the type previously described or a biased transfer roll.
  • a pressure transfer system may be employed which may include a heating and/or chemical application device for assisting in the pressure transfer and fixing of the developed image on the output copy substrate 70.
  • image transfer can be accomplished via surface energy differentials wherein the surface energy between the image and the member supporting the image prior to transfer is lower than the surface energy between the image and the substrate 70, inducing transfer thereto.
  • the image is transferred to a copy substrate via a heated pressure roll, whereby pressure and heat are simultaneously applied to the image to simultaneously transfer and fuse the image to the copy substrate 70.
  • a heated pressure roll whereby pressure and heat are simultaneously applied to the image to simultaneously transfer and fuse the image to the copy substrate 70.
  • the fusing or so-called fixing system may operate using heat (by any means such as radiation, convection, conduction, induction, etc.), or other known fixation process which may include the introduction of a chemical fixing agent. Since the art of electrostatographic printing is well known, it is noted that several concepts for transfer and/or fusing which could be beneficially used in combination with the image-wise charging system of the present invention have been disclosed in the relevant patent literature.
  • Figure 1 illustrates a simple blade cleaning apparatus for scraping the imaging member surface as is well known in the art.
  • Alternative embodiments may include a brush or roller member for removing toner from the surface on which it resides.
  • the removed toner associated with the background image is transported to a toner sump or other reclaim vessel so that the waste toner can be recycled and used again to produce the toner cake in subsequent imaging cycles.
  • imaging member 10 is provided in the form of a belt entrained about a pair of roll members including a drive roller driven by a conventional motor device (not shown) for advancing the belt in a process direction along a curvilinear path, thereby transporting the imaging member 10 through various processing stations disposed about the path of movement thereof.
  • a neutrally charged toner cake is deposited on an uncharged imaging member 10 via a toner supply apparatus 50 including a fountain-type applicator 51 in combination with a metering roll 53.
  • Metering roll 53 includes a peripheral surface situated in close proximity to the surface of imaging member 10, preferably rotated in a direction opposite to the direction of movement of the imaging member 10, providing a shear force against the toner layer deposited on the surface of the imaging member, for controlling the thickness of the toner layer thereon.
  • the metering roll 53 meters a predetermined amount of developing material (which may include toner particles immersed in liquid carrier). The excess material eventually falls away from the metering roll and may be transported to a sump for reuse in the toner applicator 51.
  • the neutrally charged toner layer deposited on the imaging member 10 is subsequently advanced to a charging station, shown to include a corona charging device 30.
  • the corona charging device 30 applies a charge through the neutrally charged toner layer 58 to the surface of the imaging member 10 such that both the imaging member 10 and the toner layer 58 will become charged.
  • the imaging member attracts ions through the toner layer in order to become charged.
  • some ions will be captured by the toner layer 58, generating a similar, albeit weaker, polarity charge therein, as illustrated by the negatively charged toner particles in Figure 4.
  • image exposure apparatus 40 which, in the case of a photoreceptive imaging member 10, selectively dissipates the charged areas of the imaging member 10 to create an electrostatic latent image thereon.
  • image exposure apparatus 40 may be positioned so as to irradiate imaging member 10 through toner layer 58 (as shown), or may be positioned so as to irradiate imaging member 10 from the underside of the imaging member 10, such that image exposing light is not required to travel through the toner layer.
  • a layer of charged toner particles is positioned on the surface of a latent image bearing imaging member 10.
  • the charged toner layer 58 is advanced past a broad beam ion source 60, represented in Figure 4 as a scorotron.
  • the scorotron introduces free mobile ions in the vicinity of the charged latent image, generating an image-wise ion stream in the presence of the latent image on the imaging member 10, as described in greater detail herein with respect to Figure 2.
  • image separator 20 is also provided in the form of a belt member entrained about a pair of opposed rollers.
  • the image separator 20 is preferably driven by contact engagement with the toner imaging member 10, although a drive device could also be coupled to one of the rollers for providing transport motion to the image separator belt.
  • electrical bias may be applied to the roll member adjacent the imaging member in a manner disclosed with respect to Figure 1.
  • electrical bias can be applied directly to the belt via a brush or well known commutator brush-type system.
  • Such a commutator brush system may be desirable to permit voltage variations in the nip 12 formed between the imaging member 10 and the image separator 20, thereby enabling a field tailoring approach similar to that disclosed in the prior art, as for example in commonly assigned U.S. Pat. Nos. 5,198,864 and 5,428,429, hereby incorporated by reference into the present patent application.
  • the embodiment of Figure 4 contemplates that the image separator 20 can be used to remove image background areas form the toner layer 58.
  • the image separator 20 is biased so as to attract image background areas from the imaging member 10, thereby maintaining toner segments corresponding to image areas on the surface of the imaging member 10.
  • the toner segments on image separator 20 are transported to a cleaning device 90, embodied as a roll member, while developed image areas remaining on the imaging member 20 are transported to a transfer station as typically found in a conventional electrostatographic printing machine.
  • the toner segments making up the image are transferred to a copy substrate via any method which may be known in the art.
  • the transferred image may thereafter be fused to the copy substrate at fusing station 100 and transported to an output device for retrieval by a machine operator.
  • the present invention provides a novel image development method and apparatus, whereby image-wise charging is accomplished by a wide beam ion source such that free mobile ions are introduced in the vicinity of an electrostatic latent image coated with layer of developing material.
  • the latent image causes the free mobile ions to flow in an image-wise ion stream corresponding to the latent image, which, in turn, leads to image-wise charging of the toner layer, such that the toner layer itself becomes the latent image carrier.
  • the latent image carrying toner layer is subsequently developed and transferred to a copy substrate to produce an output document.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electrophotography Using Other Than Carlson'S Method (AREA)
  • Wet Developing In Electrophotography (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
  • Dry Development In Electrophotography (AREA)
EP98304855A 1997-06-27 1998-06-19 Développement d'un image électrostatique Expired - Lifetime EP0887714B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US08/883,292 US5826147A (en) 1997-06-27 1997-06-27 Electrostatic latent image development
US883292 1997-06-27

Publications (3)

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EP0887714A2 true EP0887714A2 (fr) 1998-12-30
EP0887714A3 EP0887714A3 (fr) 1999-08-25
EP0887714B1 EP0887714B1 (fr) 2003-12-03

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US (1) US5826147A (fr)
EP (1) EP0887714B1 (fr)
JP (1) JPH1124378A (fr)
DE (1) DE69820160T2 (fr)

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Also Published As

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DE69820160D1 (de) 2004-01-15
EP0887714B1 (fr) 2003-12-03
DE69820160T2 (de) 2004-09-09
EP0887714A3 (fr) 1999-08-25
JPH1124378A (ja) 1999-01-29
US5826147A (en) 1998-10-20

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